JP2024528484A - Optical module comprising a camera and a light-absorbing opaque element - Google Patents

Abstract

The invention relates to an optical module (1) for a vehicle, said optical module (1) comprising: - a camera (10) having a set of optical lenses (100); - a housing (11) configured to receive said camera (10); and - a glass window (12) arranged facing said camera (10) and configured to hide said camera (10) from the outside of the vehicle, characterized in that said optical module (1) further comprises an opaque element (13) configured to absorb light (Lx) from the outside of the vehicle (2) so as to reduce stray light reflections of said light (Lx) at the set of optical lenses (100) of said camera (10).

Description

The present invention relates to an optical module for a vehicle. It is particularly, but not exclusively, applicable to motorized vehicles.

As shown in FIG. 1, an example of an optical module 6 for a vehicle known to those skilled in the art comprises:
a camera 60 equipped with a set of optical lenses 600,
a housing 61 adapted to receive said camera 60;
an outer lens 62 arranged facing said camera 60;

The outer lens 62 is opaque, which makes it possible to hide the camera 60 from outside the vehicle. An observer outside the vehicle therefore does not see the camera 60 when looking at the optical module 6. The camera 60 is used to monitor the vehicle's external environment. It generates an image of the vehicle's external environment, an image that is useful to the driver of the vehicle, in particular when parking said vehicle. The vehicle displays the image from the camera 60 on its on-board screen.

One disadvantage of this prior art is that the light Lx coming from outside the vehicle, especially the light coming from above, is reflected on the set of optical lenses 600 towards the inner surface 620 of the outer lens 62, which results in primary reflections r1 as shown in FIG. 1. These primary reflections r1 are reflections of order 1. These primary reflections r1 are in turn reflected on the inner surface 620 of said outer lens 62, which results in secondary reflections r2 that are returned to the set of opaque lenses 600 as shown in FIG. 1. These secondary reflections r2 are reflections of order 2. These secondary reflections r2 cause parasitic diffusion of the light Lx inside the set of optical lenses 600, which is called flare. Drivers will see these secondary reflections r2 on the image generated by the camera 60, which is visually distracting to the driver who is viewing the image from the camera 60 on the in-vehicle screen. This makes it difficult for them to park the vehicle.

In this regard, the present invention aims to provide an optical module that makes it possible to overcome the aforementioned drawbacks.

To this end, the invention proposes an optical module for a vehicle, said optical module comprising:
a camera equipped with a set of optical lenses,
a housing adapted to receive said camera;
an outer lens arranged facing the camera and configured to hide the camera from outside the vehicle, characterized in that the optical module further comprises an opaque element configured to absorb light coming from outside the vehicle so as to reduce parasitic reflections of the light on the set of optical lenses of the camera.

According to non-limiting embodiments, the optical module may further include one or more of the following additional features, implemented alone or in any combination technically possible:

According to one non-limiting embodiment,
According to one non-limiting embodiment,
According to one non-limiting embodiment, the parasitic reflection is caused by reflection of light on the inner surface of the outer lens.

According to one non-limiting embodiment, the opaque element is the outer lens, the outer lens including a first portion and a second portion and being opaque in a non-homogeneous manner.

According to one non-limiting embodiment, the first portion of the outer lens is more opaque than the second portion.

According to one non-limiting embodiment, the first portion is darker than the second portion.

According to one non-limiting embodiment, the first portion has a greater thickness than the second portion.

According to one non-limiting embodiment, the first portion is made of a material that absorbs more light than the material of the second portion.

According to one non-limiting embodiment, the first portion of the outer lens is between 30% and 50% opaque.

According to one non-limiting embodiment, the second portion of the outer lens is 75% to 80% transparent.

According to one non-limiting embodiment, the first portion of the outer lens is positioned at an angle of 11° or greater relative to the optical axis of the camera.

According to one non-limiting embodiment, the first portion of the outer lens is positioned at an angle of 21° or greater relative to the optical axis of the camera.

According to one non-limiting embodiment, the opaque element is an opaque cap positioned to protrude from the housing of the camera.

According to one non-limiting embodiment, the opaque element is an opaque cap positioned over the set of optical lenses of the camera.

According to one non-limiting embodiment, the housing has a non-reflective inner surface.

According to one non-limiting embodiment, the light is natural light or light from a street lamp.

According to one non-limiting embodiment, the first portion of the outer lens is 30% to 50% opaque and the second portion of the outer lens is 75% to 80% transparent.

According to one non-limiting embodiment, the first portion of the outer lens is 50% opaque and the second portion of the outer lens is 80% transparent.

According to one non-limiting embodiment, the first portion of the outer lens is opaque in a variable manner.

According to one non-limiting embodiment, the first portion of the outer lens has a thickness greater than 2 mm and the second portion has a thickness substantially equal to 2 mm.

According to one non-limiting embodiment, the first portion is positioned at an angle of 11° to 25° relative to the optical axis of the camera.

The invention and its various applications will be better understood by reading the following description and examining the accompanying figures, in which:
FIG. 1 is a schematic diagram of a prior art optical module for a vehicle, the optical module comprising a camera, a housing for the camera, and an outer lens. FIG. 2 is a schematic diagram of an optical module for a vehicle according to the invention, said optical module comprising a camera, a housing for said camera, an outer lens and an opaque element. FIG. 3 is a schematic side view of the optical module of FIG. 2 according to a first alternative embodiment of the first non-limiting embodiment, according to which the outer lens and the opaque element are combined. FIG. 4 is a schematic side view of the optical module of FIG. 2 according to a second alternative embodiment of the first non-limiting embodiment, according to which the outer lens and the opaque element are combined. FIG. 5 is a schematic side view of the optical module of FIG. 2 according to a third alternative embodiment of the first non-limiting embodiment, according to which the outer lens and the opaque element are combined. FIG. 6 is a schematic side view of the optical module of FIG. 2 according to a first alternative embodiment of a second non-limiting embodiment, according to which the outer lens and the opaque element are separate elements. FIG. 7 is a schematic side view of the optical module of FIG. 2 according to a second alternative non-limiting embodiment, according to which the outer lens and the opaque element are separate elements. FIG. 8 is a schematic side view of the optical module of FIG. 2, according to one non-limiting embodiment, where the optical module is positioned at a distance from a street light.

Elements that are identical in terms of structure or function and that appear in different figures retain the same references unless otherwise noted.

The optical module 1 for a vehicle 2 according to the invention will be described with reference to Figures 2 to 8. In one non-limiting embodiment, the vehicle 2 is a motorized vehicle. Motorized vehicle is understood to mean any type of motor-driven vehicle. This embodiment will be taken as a non-limiting example throughout the remainder of the specification. Therefore, in the remainder of this specification, the vehicle 2 will be referred to as a motorized vehicle 2.

As shown in FIG. 2, an optical module 1 for a motor vehicle 2 comprises:
- camera 10,
a housing 11,
an outer lens 12 , and an opaque element 13 .

The camera 10 comprises a set of optical lenses 100. The set of optical lenses 100 includes one or more optical lenses. The camera 10 has a field of view Fov. The camera 10 generates an image i1 of the external environment of the motor vehicle 2. In other words, it generates an image i1 of a scene in the external environment. Thus, the camera 10 detects moving objects such as other vehicles, pedestrians, bicycles, or stationary objects such as sidewalks, road signs, buildings, trees, etc. In one non-limiting example, the image i1 is displayed on the dashboard of the motor vehicle 2, allowing the driver of the motor vehicle 2 to perform a maneuver to park the motor vehicle 2. In another non-limiting example, the image i1 allows the driver to see vehicles at the intersection that may come from the right and left to determine whether they can cross the intersection safely. In another non-limiting example, the image i1 is an image from a reverse camera. This allows them to see pedestrians behind the motor vehicle 2, thus allowing the driver to perform a reverse maneuver completely safely without running over the pedestrians. The camera 10 further comprises an optical sensor 101 associated with the optical lens 100, the optical sensor 101 having an integration time t1. The integration time t1 is the opening time of the cell of the optical sensor 101.

In one non-limiting embodiment, the camera 10 is an HDR, or "high dynamic range," camera, and has multiple integration times t1. An HDR camera allows three images of a scene captured simultaneously to be reconstructed to produce a single final image free of noise, particularly with different integration times t1. This also improves the optical contrast of the final image, so that there is more detail in the final image.

In one non-limiting embodiment, the camera 10 is a wide-angle camera. In one non-limiting example, the camera 10 has a total horizontal angle of 170° relative to the vehicle axis Ax. In a non-limiting embodiment, the camera 10 is located at the front, rear, or one side of the motorized vehicle 2. In a non-limiting embodiment, the camera 10:
- in the logo at the front of the motor vehicle 2, or - in the front headlamps, or - in the tail lamps, or - in the rear bumper, or - in the rear-view mirror,
To be placed.

The housing 11 is configured to receive the camera 10. It is closed by an outer lens 12. In one non-limiting embodiment, the inner surface 11b of the housing 11 is black and non-reflective. To make it non-reflective, in one non-limiting embodiment, it is covered with a matte paint. This allows the camera 10 to be hidden from the outside of the motor vehicle 2. Thus, observers outside the motor vehicle 2 do not see the camera 10 even if they look at the optical module 1.

An outer lens 12, called a protective lens, is arranged facing the camera 10. It is configured to hide the camera 10 from the exterior of the motor vehicle 2. The camera 10 is therefore invisible to an observer outside the motor vehicle 2 looking at the optical module 1. The outer lens 12 is therefore opaque. In a non-limiting embodiment, the outer lens 12 has an opacity substantially equal to 20% (in other words, a transparency substantially equal to 80%). The outer lens 12 has an inner surface 120 directed towards the camera 10 and an outer surface 121 opposite the inner surface 120 and directed towards the exterior of the motor vehicle 2. In a non-limiting embodiment, the outer lens 12 closes the housing 11.

The opaque element 13 is configured to absorb light Lx coming from outside the motor vehicle 2 so as to significantly reduce or completely eliminate parasitic reflections of said light Lx (see r2 in FIG. 1 showing the prior art) at the set 100 of optical lenses of the camera 10.

The light Lx coming from outside is called external light Lx. This light Lx can be natural light from the sun (otherwise called zenith light) or light from street lamps. It is light coming from above with respect to the optical axis Aa of the camera 10. In one non-limiting embodiment, the optical axis Aa of the camera 10 corresponds to the optical center of the set of optical lenses 100.

As will be seen below, the opaque element 13 may be combined with or distinct from the outer lens 12. In FIG. 2, the opaque element 13 is shown diagrammatically separated from the outer lens 12.

In a first non-limiting embodiment shown in Figures 3 to 5, the opaque element 13 is the outer lens 12. Thus, the opaque element 13 and the outer lens 12 are combined. The outer lens 12 comprises a first portion 12a, also called upper portion 12a, and a second portion 12b, also called lower portion 12b, which is opaque in a non-homogeneous manner.

In one non-limiting embodiment, the first portion 12a and the second portion 12b are positioned to cover the field of view Fov of the camera 10.

The first portion 12a is configured to receive the light Lx directly, while the second portion 12b is configured to receive a small portion of the light Lx directly, or not receive the light Lx directly. Thus, the upper portion 12a is located above the lower portion 12b along an axis Az perpendicular to the vehicle axis Ax. It is noted that the light Lx may be reflected by the ground on which the motor vehicle 2 is positioned, in particular to reach the second portion 12b. Thus, the second portion 12b receives the light Lx, but mainly or entirely indirectly through its reflection on the ground. It is noted that reflections from the ground hardly produce any flare. Thus, the sources of these reflections are street lamps and the sun. Other sources may be other vehicles.

In one non-limiting embodiment, the upper portion 12a thus extends from the top 110 of the housing 11 to approximately the mid-height of the camera 10, in other words approximately to the optical axis Aa of the camera 10; the lower portion 12b extends from the bottom 111 of the housing 11 to approximately the mid-height of the camera 10, in other words approximately to the optical axis Aa of the camera 10.

In one non-limiting embodiment, the upper portion 12a and the lower portion 12b are flat.

As shown in FIG. 8, in a non-limiting embodiment, the camera 10 focuses up to a maximum viewing distance D1 of 20 meters. In the worst case, the camera 10 may be dazzled by the light Lx coming from the street lamp 4 shown in FIG. 8 at an angle β=Arctan(D2/D1) where D2=size of the street lamp 4 minus height h1 of the camera 10 relative to the ground 5. In a non-limiting exemplary embodiment, the camera 10 is placed at a height h1 of 1 meter relative to the ground 5. This is the case for a camera 10 for panoramic vision, called a "surround view camera". In a non-limiting embodiment, the street lamp 4 has a size D0 of 5m to 9m in height. Therefore, β=Arctan(4/20)=11°, and 4=5m-1m. Therefore, in a non-limiting embodiment, the first portion 12a is placed at an angle β of 11° or more relative to the optical axis Aa of the camera 10. That is, the lower end of the first portion 12a stops beyond the angle β of 11°.

It is noted that the illuminance of the street lamp 4 is about 500 lux or 40500 cd (candela) for a street lamp with a height of 5 m. At a viewing distance D1 of 20 m, the illuminance is almost equal to 100 lux, which is very small. On the other hand, at a viewing distance D1 of 10 m, the illuminance is about 250 lux. Thus, the light Lx coming from such a street lamp 4 produces a stronger flare effect when the viewing distance D1=10 m than when the viewing distance D1=20 m. Furthermore, in another non-limiting embodiment, the first portion 12a is disposed at an angle β of 21° or more with respect to the optical axis Aa of the camera 10.

In one non-limiting embodiment, the first portion 12a is disposed at an angle β of 11° to 25° relative to the optical axis Aa of the camera 10.

The first part 12a of the outer lens is more opaque than the second part 12b and therefore absorbs more light Lx, whereas the second part 12b is more transparent and therefore captures more light Lx, especially reflected from the ground, and more direct light Lx if it receives the same.

In one non-limiting embodiment, the first portion 12a is 30% to 50% opaque (in other words, 70% to 50% transparent), while the second portion 12b is 75% to 80% transparent (in other words, 20% to 25% opaque). In an alternative non-limiting embodiment, the first portion 12a is 50% opaque (in other words, 50% transparent) and the second portion is 80% transparent (in other words, 20% opaque). This means that the first portion 12a blocks up to 50% of the light Lx, while the second portion 12b transmits 80% of the light Lx that reaches the optical module 10.

In a non-limiting embodiment, the first portion 12a is opaque in a variable manner. Thus, in a non-limiting example, the opacity of the first portion 12a may gradually increase from bottom to top, in other words, from an end located near the optical axis Aa of the camera 10 to an end located near the top 110 of the housing 11. Similarly, in a non-limiting embodiment, the second portion 12b is transparent in a variable manner. Thus, in a non-limiting example, the transparency of the second portion 12b may gradually increase from top to bottom, in other words, from an end located near the optical axis Aa of the camera 10 to an end located near the bottom 111 of the housing 11.

The upper portion 12a absorbs the light Lx so that it passes only partially through the outer lens 12 at this level and so that there is very little or no parasitic reflection on the inner surface 120 of the outer lens 12 that disturbs the image i1 from the camera 10. As shown in Figures 3 to 5, the upper portion 12a absorbs most of the light Lx' and passes a small portion Lx''. The upper portion 12a also significantly reduces or even eliminates other parasitic reflections, which are other secondary reflections on the set of optical lenses 100 and which originate from reflection of the external light Lx inside the outer lens 12, in other words directly on its inner surface 120, and are returned to the set of optical lenses 100.

Three non-limiting alternative embodiments for making the first portion 12a of the outer lens 12 more opaque than the second portion 12b are described below.

In a first non-limiting alternative embodiment shown in FIG. 3, the first portion 12a is darker than the second portion 12b. This makes it more opaque. It is noted that in order to make the first portion 12a darker than the second portion 12b, in one non-limiting embodiment, the upper portion 12a is darkened in an industrial process. Thus, instead of 20% opaque, in one non-limiting example, the upper portion 12a is 30% opaque. In another non-limiting embodiment, the lower portion 12b is made more transparent. Thus, instead of 70% transparent as the upper portion 12a, the lower portion 12b is 90% transparent in one non-limiting example. To darken the upper portion 12a, in one non-limiting example, a pigmented paint may be used. In another non-limiting example, a 2K or 3K multi-shot injection molding process may be used.

In a second alternative non-limiting embodiment shown in FIG. 4, the first portion 12a has a thickness e1 that is greater than the thickness e2 of said second portion 12b. The thicker the material of the first portion 12a, the more opaque it is, and therefore the more light Lx it absorbs. In one non-limiting embodiment, the thickness e1 is greater than 2 mm. In one non-limiting embodiment, it is equal to 3 mm to obtain 50% opacity. In one non-limiting embodiment, the thickness e2 is substantially equal to 2 mm.

It is noted that the material absorbs light according to a linear absorption coefficient α, which is P=P0×exp(-α×e), where e is the thickness of the material, where e=e1 is the thickness of the material of the first portion 12a, P is the luminous power of the light Lx, and P0 is the initial light power. Thus, α=(4×π×k)/λ, where λ is the wavelength of the light Lx, and k is the attenuation coefficient specific to the material of the first portion 12a. k depends on the refractive index and dielectric constant of the material. The formulation of k is known to those skilled in the art, so k will not be described here.

In a third alternative non-limiting embodiment shown in FIG. 5, the first portion 12a is made of a material m1 that absorbs more light Lx than the material m2 of the second portion 12b. In one non-limiting example, the lower portion 12b is made of a PMMA (polymethylmethacrylate) or PC (polycarbonate) material. In one non-limiting example, the upper portion 12a is made of a PMMA or PC material that has more color pigments (shown as dots) therein that absorb light Lx, thereby making it more opaque.

6 and 7, the opaque element 13 is an opaque cap, distinct from the outer lens 12. They are therefore not combined. In this second non-limiting embodiment, in one non-limiting example, the outer lens 12 is 20% opaque, thereby capturing 80% of the light Lx coming from outside the motor vehicle 2. In one non-limiting embodiment, the opaque cap 13 is flat. The opaque cap 13 is positioned so as not to obstruct the field of view Fov of the camera 10.

In a first alternative non-limiting embodiment shown in FIG. 6, the opaque cap 13 is positioned to protrude from the housing 11 of the camera 10. It extends from the top 110 of the housing 11 parallel to the optical axis Aa of the camera 10. As can be seen, the opaque cap 13 absorbs light Lx. It absorbs light partially or totally, depending on its opacity. In the non-limiting example shown, it completely absorbs light. In one non-limiting example, the opaque cap 13 is adhesively bonded to the housing 11.

In a second non-limiting alternative embodiment shown in FIG. 7, an opaque cap 13 is placed above the set of optical lenses 100 of the camera 10. It extends parallel to the optical axis Aa of the camera 10. As can be seen, the opaque cap 13 absorbs light Lx. It absorbs light partially or totally. This depends on its opacity. In the non-limiting example shown, it absorbs light completely. In one non-limiting embodiment of this second non-limiting alternative embodiment, the opaque cap 13 is placed against the outer lens 12. In one non-limiting example, it is adhesively bonded to the outer lens 12.

It is noted that in a camera without an opaque element 13, the darker the scene, the longer the integration time t1 must be to capture and generate an image i1 of said scene, and the brighter the scene, the shorter the integration time t1 must be. Furthermore, without the opaque element 13, multiple integration times t1 are required to arrive at a final image i1 with strong contrast between the various areas of the image, where details can be clearly seen in all areas of the imaged scene. For example, a short integration time t1 is required to image clouds in the sky brighter than the road (the dark elements of the image are darkened) and a long integration time t1 is required to image a road bump darker than the sky (the sky is saturated and thereby almost pure white).

In image i1, the light intensity of the scene is greater towards the top (at sky level) than in the parts at the optical axis Aa of the camera 10 and towards the ground. The opaque element 13 makes it possible to compensate for this difference in light intensity. The light intensity becomes more uniform throughout the image i1 produced by the camera 10. The opaque element 13 makes it possible to darken the upper part of the image i1. With a single integration time t1 in image i1, instead of using multiple integration times t1, it is possible to clearly see details in all areas of the image i1, in particular at the top of the imaged scene and also at the bottom of the imaged scene. In this way, the contrast between the various elements in image i1 is reduced by the opaque element 13.

It is also noted that in a camera without opaque element 13, increasing the contrast in image i1 reduces the signal-to-noise ratio of optical sensor 101. In particular, without opaque element 13, for a given integration time t1, an image is obtained with larger quantification errors towards the extremes of light intensity. With opaque element 13, the signal-to-noise ratio is improved since the quantification noise at the extremes of light intensity is reduced. Thus, conventional HDR using multiple images with different integration times t1 is not necessary.

In this way, the use of opaque element 13 reduces the contrast of image i1 and improves the signal-to-noise ratio, which allows more details to be seen in image i1. Thus, a driver looking at image i1 from camera 10 sees the details more clearly, which makes maneuvering easier, for example when parking.

Of course, the description of the invention is not limited to the above-mentioned embodiments and fields. Thus, in one non-limiting embodiment, the set of optical lenses 100 may be treated with an anti-reflection treatment. Thus, in another non-limiting embodiment, instead of extending from the top of the housing 11 to approximately the mid-height of the camera 10, the upper portion 12a may extend from the top 110 of the housing 11 to 1/3 of the camera 10.

Thus, the described invention has, inter alia, the following advantages:
it is possible to significantly reduce or even eliminate the parasitic reflections in the set of optical lenses, the parasitic reflections caused by the light Lx; it is therefore possible to reduce or even eliminate the flare, which is not annoying to the driver of the vehicle 2 when viewing the images from the camera,
- it makes it possible to hide the camera 10 from an observer looking at the optical module 1 from outside the motor vehicle 2;
it makes it possible to obtain a more homogeneous image and therefore to reduce the contrast in image i1, thereby making it possible to obtain a better image rendering quality;
It is possible to increase the signal-to-noise ratio, especially in the dark areas which are generally located towards the bottom of the image i1.

Claims (15)

An optical module (1) for a vehicle (2), said optical module (1) comprising:
a camera (10) equipped with a set of optical lenses (100),
a housing (11) adapted to receive said camera (10);
an outer lens (12) arranged facing said camera (10) and configured to hide said camera (10) from the outside of said vehicle (2), characterized in that said optical module (1) further comprises an opaque element (13) configured to absorb light (Lx) coming from the outside of said vehicle (2) so as to reduce parasitic reflections of light (Lx) at the set of optical lenses (100) of said camera (10);
An optical module (1) comprising: The optical module (1) of claim 1, wherein the parasitic reflection is caused by reflection of light (Lx) on the inner surface (120) of the outer lens (12). The optical module (1) according to claim 1 or 2, wherein the opaque element (13) is the outer lens (12), the outer lens (12) comprising a first portion (12a) and a second portion (12b) and being opaque in a non-homogeneous manner. The optical module (1) of claim 3, wherein the first portion (12a) of the outer lens (12) is more opaque than the second portion (12b). The optical module (1) of claim 4, wherein the first portion (12a) is darker than the second portion (12b). The optical module (1) of claim 4, wherein the first portion (12a) has a thickness greater than the second portion (12b). The optical module (1) according to claim 4, wherein the first part (12a) is made of a material (m1) that absorbs more light (Lx) than the material (m2) of the second part (12b). The optical module (1) according to any one of claims 4 to 7, wherein the first portion (12a) of the outer lens (12) has an opacity of 30% to 50%. The optical module (1) according to any one of claims 4 to 8, wherein the second portion (12b) of the outer lens (12) has a transparency of 75% to 80%. The optical module (1) according to any one of claims 3 to 9, wherein the first portion (12a) of the outer lens (12) is disposed at an angle (β) of 11° or more with respect to the optical axis (Aa) of the camera (10). The optical module (1) according to any one of claims 3 to 10, wherein the first portion (12a) of the outer lens (12) is disposed at an angle (β) of 21° or more with respect to the optical axis (Aa) of the camera (10). The optical module (1) according to claim 1 or 2, wherein the opaque element (13) is an opaque cap positioned protruding from the housing (11) of the camera (10). The optical module (1) according to claim 1 or 2, wherein the opaque element (13) is an opaque cap positioned above the set of optical lenses (100) of the camera (10). An optical module (1) according to any one of claims 1 to 13, wherein the housing (11) has a non-reflective inner surface (11b). An optical module (1) according to any one of claims 1 to 14, wherein the light (Lx) is natural light or light from a street lamp.

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